Method of making bifocal lenses.



\ PATENTED JUNE 16, 1908. v H. J. STEAD.

METHOD OF MAKING BIFOGAL LENSES.

APPLIUATION FILED JULYlZ, 1907.

UNITED STATES PATENT OFFICE.

HAROLD J. STEAD, OF KANSAS CITY, MISSOURI, ASSIGNOB B Y DIRECT AND MESNE ASSIGN- MENTS, TO THE STEAD LENS COMPANY, OF KANSAS CITY, MISSOURI, A CORPORATION OF MISSOURI.

IIETHOD OF MAKING'BIFOGAL LENSES.

Specification of Letters Patent.

Patented Julie 16, 1908.

Application flled July 12, 1907. Serial No. 883,628.

- sas City, in the county of Jackson and State of Missouri, have invented certain new and I useful-Improvements, in Methods of Making an .pr'o erly resecured in Bifocal Lenses, of which the followingis a specification.

This invention relates to a method of making bifocal lenses, and more especially lenses of that type composed of two pieces of glass of different density secured in superposed relation.-. i

Heretofore one method of producing bifocal lenses has been to secure the two pieces of glass together with transparent cement. Another method has been to weldsuch ieces of glass together, and I am aware that 1t has also been'contemplate dto produce lenses by blowing one of t e pieces of glass upon the other. The first method is ob ectionable because the cements-finder certain well known conditions-softensand permitswf an indeendent movement of the small piece of glass ormingl the lower field of vision, the result being t e cement assumes a wavelike appearance and renders such lower field of vision im ractical until the small iece is removed ace. An objectionjggo' -t e second method 1s the expense involved in indin each piece of glass se arately. T e third method is objectiona le because the glass has to be blown to an undesirable thickness and then ground down before their accuracy can be determined, thus involving a loss by waste of material and la.-

My object is to produce a lens preferably by blowing crown glass into a suitable mold having segmental cavities to roduce segmental glass projections of the esired curva -j tureor it can e blown into the form of a globe of *roper curvatureand then cutblow flint glass into a mold to produce a jarhavingv inwardly projecting spherical segments whose curvatures are shar er than the segmental cav1t1es 1or countersmks ofthe Y crown glass. If desired theiiint glass. may

be blown into the form of a globe, the curvature being shar er than that ofthe cavities or countersinks o the crown glass slab. The

segments or flint glass are cutfrom the jar orv part of a crown glass jar blown therein.

1 blown glass globe.

which in from the globe as the case may be, incircular form. One of such segments is then placed centrall upon the countersink of one of the,

settle down into said countersink, or this object may be accomplished in any other suitable manner, as by electric heating or otherwise.

sibility of imprisoning an air between the pieces because the flint g ass is ,of uniform thickness and therefore'melts uniformly and in its melting forces the airradially outward from the cavity or countersink of the crown glass. The bifocal blank thus produced is then cut to the required form and ground in the usual manner to produce a perfect bifocal lens.

Referring to the 'drawing,Figure 1, is a horizontal section of a part of a mold arid a 1g. 2, is a segment of a globe of crown lass; .Fig. 3, is a section of one of the Ma of crown glass after it is cut from the globe.- Fig. 4, is a face view of a segment after it is cut from thejar or globe. Fig. 5, is a horizontalseetion of a mold and of a jar of flint glass blown therein. Fig. .6 is a section of a Fig. 7, is a plan view of one of the circular pieces of flint glass. Fig. 8 is asection of the same. Fig. 9, is a section showing the crown glass blank with av-fiint glass iece resting therein. Fig. 10, is a sec- This treatment results in the production of a blank'bifoca'l lens without any pos-- tion s owing such'crown glass and flint-glass v ieces after they have been welded to ether.-

ig. -1 1, is a face view of a completed ifocal lens.

In the saiddrawing, 1 indicates a mold,

ractice wil large num er of cavities 2, in its inner'wall.'-

3 indicates a par't'of a jar of crown glass blown therein so asto r'oducethe cavities orcountersinksA. The otted lines 5, show the line of cleavage, that is the line on which the blanks of crown glass are cut from the jar,

and 6 indicates the lines on which such piece of crbwn'glass' are preferably ground when ready to receive the flint-glass, hereinafter described.

- In Fig. 2 5 indicates the lineof cleava e of the globe of crown glass and 7 indicates w ere the. crown glass blank is cut fromsaidglobe.

preferably contain a 8 indicates a mold preferably in the form of a hollow jar or casing having inwardly projectin rounded'bosses 9. 10 indicates a flint g ass jar blown therein and forming seging a clear and distinct division between the up or and lower field's of vision.

t will be understood that my invention contemplates the idea of blowing or molding flint glass disks 13, as they are termed in the trade, for welding onto crown glass slabs without regard to how such slabs are made,

and conversely contemplates the use of blown or molded crown glass slabs without regard to how the flint glass disks are made. I also contemplate the making in any way of crown glass slabs provided with countersinks and the pouring of molten flint glass into such cavities and then grinding both glasses to produce the complete lens.

From the above description it will be apparent that I have evolved a process formaking bifocal lenses possessing the features of advantage enumerated as desirable and I wish it to be understood that I do not desire to be restricted to the exact methods of construction and treatment described, as it is obvious changes may be made which will not be a departure from the spirit and scope of the invention.

Having thus described the invention what I claim as new and desire to secure by'Letters Patent is 1., The method of making bifocal lenses, the same consisting in blowing crown glass into a hollow mold having a rounded cavity or countersink in its inner side, then cutting a section from the crown glass on a line surrounding said cavity, then placing a flint glass disk upon the section of crown glass directly over said countersink, and then welding the crown glass section and the flint gl disk together by heating them until the flint glass disk settles down into and fills said countersink.

2. The method of making bifocal lenses, the same consisting in blowing crown glass into a hollow mold having a rounded cavity or countersink in its inner side, then cutting a section from the crown glass on a line surrounding said cavity, then placing a flint glass disk upon the section of crown glass directly over said countersink, then welding the crown glass section and the flint glass disk together by heating them until the flint glass disk settles downinto and fills said countersink, and then grinding the bifocal blank thus produced into a bifocal lens.

3. The method of making bifocal lenses, the same consisting in. blowing flint glass into a hollow mold having an inwardly projecting rounded portion on its inner side,

then cutting a section-usually termed a diskfrom the blown glass on a line surrounding said projection, then placing said flint glass disk upon a crown glass section having a countersink in its upper side and directly underlying the flint glass disk, and then welding the crown glass section and the flint glass disk to ether by heating them until the flint glass disk settles down into and fills the countersink. p

4., The method of making bifocal lenses, the same consistin -in blowing flint glass into a hollow mold aving. an inwardly projecting rounded portion on its inner side, then cutting a sectionusually termed a disk-from the blown glass on a line surrounding said projection, then placing said fiint glass disk upon a crown glass section having a countersink in its upper side and directly underlying the flint.glass disk, then welding the crown glass section and the flint glass, disk together by heating them until the 'nt glass disk settles down into and fills the countersink, and then grinding the-bifocal blank thusproduced into a bifocal-lens.

5. The method of making bifocal lenses, the same consisting in blowing crown glass into a hollow moldhaving a rounded cavity or countersink in its inner side, then cutting a section from the crown glass on a line surrounding said cavity, then blowing flint glass into a hollow mold havingan inwardly projecting rounded portion of sharper radius or curve than said countersink, then cutting a section-usually termed a disk-from the flint glass on a line surrounding said' projection then placing the flint glass disk with its convex'side down upon the crown glass section directly over and depending partially into said countersink, and then welding the crown glass section and the flint glass disk together by heating them until the flint glass disk settles down into and completely fills the countersink.

6. The method of making bifocal lenses, the same consisting-in blowingierown glass into a hollow mold having a rounded cavity or countersink in its inner side, then cutting a section from the crown glass on a line surrounding said cavity, then blowing flint irs glass into a hollow mold having an inwardly projecting rounded portion of sharper radius or curve than said countersink, then cutting a section-usually termed a disk-from the flint glass on a line surrounding said projection, then placing the flint glass disk with its convex side down upon the crown glass section directly over and depending aao,sis 8 partially into said countersink, then' Welding In testimony whereof I efiix mysignature, the ir'own glass section and the flint glass in the presence of two witnesses. di'sk ogether by heating themnntil the flint v lass d sk settles down into and completely HAROLD E 5i fills-the countersink, and then grinding the Witnesses:

bifocal blank thus produced into, a bifocal j H. C. RODGERS,

lens. G. Y. THORPE. 

